add method
Returns a copy of this with the duration
added.
Contract
Throws a RangeError if the result is outside the valid range.
Example
Offset(16).add(Duration(hours: 2)); // Offset(18)
Offset(18).add(Duration(hours: 2)); // throws RangeError
Implementation
@Possible({RangeError})
@useResult Offset add(Duration duration) => Offset.fromMicroseconds(_microseconds + duration.inSeconds * 1000 * 1000);